how to bend a zipper to the contour of a jacket?
Here's one way:

With the low poly object selected, go into Edit mode and select an edge loop that runs the length of the object(top to bottom). Press Shift + D then Esc to duplicate the the edge loop. Now press P and choose Selection to make the duplicate edge loop a separate object. Go back to Object mode and select the edge loop object. Press Alt + C and choose Curve from Mesh to make it into a Curve object. Select the zipper and add a Curve modifier to it with the edge loop object as the curve object and Z as the axis. Move the zipper on the Z axis until it fits the curve as you want.